1. Field of the Invention
The present invention relates to launder systems for supplying molten metal from a source of molten metal to a casting mould or a secondary process, and is particularly concerned with the launder nozzle.
2. Description of Related Art
It is current practice to melt a metal in a crucible and to supply the molten metal from the crucible to one or more casting moulds or to a secondary process. The molten metal is supplied along launders which have one or more channels to interconnect the crucible and the casting moulds or secondary process.
It is known to incorporate devices to remove or reduce the amount of inclusions present in the molten metal passing along the launder, so as to clean the molten metal and thereby improve the integrity of finished cast articles.
One way of achieving this is to provide one or more dams or weirs in the launder to trap the inclusions. However, some inclusions can still be carried through to the casting mould or secondary process.
Another way of achieving this is to provide a fixed filter in the launder. This is more efficient at cleaning the molten metal than the dams. However, the provision of the filter in the launder increases the possibility of blockages occurring which can result in the scrapping and remaking of the launder.
In some launders a ceramic lining is cemented into the launder, and is normally replaced after each casting operation.
In some crucibles a ceramic lining is provided, and it is usual practice with such crucibles to have a wash out melt which cleans the surface of the ceramic lining and removes any loose debris. Thus it can be seen that presently used launders are used only once and are wasteful of their ceramic linings.